In order to form electrical connections with the electrodes of a capacitor, particularly a capacitor of the kind wherein a laminate comprising interleaved electrode and dielectric strips is formed as a roll, various means are used in the prior art. For example, tap straps may be used. Another well-known technique is schooping, which is essentially a process whereby a conductive coating, usually a molten metal such as aluminum or zinc, is sprayed or otherwise applied to exposed portions of the capacitor electrodes to make a connection therewith. It is not uncommon for metal particles from the spray to penetrate into the capacitor during the schooping process. If these particles contact the opposite electrode, i.e., the electrode with which contact is not desired at the particular end of the capacitor, a short may result which can cause capacitor failure to occur. Additionally, even if no actual contact is made, the mere presence of the schooping particles near the capacitor end provides conductive material that increases the likelihood of arc-over from one electrode to another.
Where an electrode consists of a dielectric strip whose surfaces are metallized, short circuits do not as a rule occur if schooping is used at the roll ends. This is due to the self-clearing capability of such an electrode, which causes the stray metal particles coming into contact therewith to vaporize a small portion of the metallized surface. Such electrodes are thus cleared almost instantaneously, preventing capacitor failure. However, where an electrode consists of a metal foil, no such self-clearing capability exists and a short circuit may develop when a stray particle of the conductive coating makes contact therewith.
Although a sprayed metal connection at both ends of a rolled capacitor is preferred for reasons of economy, persistent failures due to the above-mentioned shorting have heretofore limited the use of schooping to establish electrical connections with the electrodes. In the prior art, a commonly used technique for minimizing the entry of the particles into the roll comprises schooping the roll ends at an oblique angle, i.e. to spray the molten particles obliquely onto the roll ends. Experience has shown that capacitor failure is not significantly reduced or eliminated with this technique.